In order to prove the authenticity of objects and to be able to differentiate objects from forgeries, these are provided with complex, forgery-proof, visually and/or automatically testable security elements. Objects particularly worthy of protection are documents of value, in particular bank notes, checks, check cards, credit cards, identity cards, passports, admission tickets, tickets for public transport and the like.
The more complex the security elements and the more elaborate the production of them, the higher the forgery protection. One security element often combines several different security features which are partly hidden and therefore only machine-readable or discernible with the help of additional apparatus and which are partly visible to the naked eye so as to enable a visual test. The combination of several security features in one security element is not always easily to realize and from time to time involves compromises, which cause particular security features to no longer be able to develop their optimal effect.
For example, from WO 01/03945 A1 a multilayer security element for security documents, bank notes and credit cards is known, which combines a layer with embossed diffraction structures with a color shift layer. Here color shift effect means the effect of color change from different viewing angles. Each of both security features offers effective copy protection and has optical effects easily to visually test. Additionally, both security features can only be imitated with great efforts. The optical effect of embossed holograms is substantially enhanced when the diffraction structures are viewed in front of a reflecting background, and the color shift effects, too, are brought out especially intensively in front of a specularly reflective background. Therefore, in WO 01/03945 A1 is, among other things, proposed to combine the layer provided with diffraction structures and the color shift effect layer with a common reflective metal background layer. This reflective metal background layer can additionally have magnetic properties so that a further third magnetic security feature is integrated in the security element.
The problem with a reflective background coating with magnetic properties is the fact that magnetic materials as a rule have poor reflection properties. Those with acceptable reflection properties, however, have less distinct magnetic properties. In EP 0 341 002 B1 a thin-layer structure with a color shift effect layer and a magnetic metal background coating of a cobalt nickel alloy is proposed as security element. Such a background coating should have acceptable reflection properties as well as good magnetic properties. Nonetheless, the reflection properties are not optimally.